NEW YORK (CNN/Money) - Former Sotheby's chairman Alfred Taubman was found guilty Wednesday of conspiring with the auction house's chief competitor to fix the commissions paid by fine-art sellers.

The jury of eight men and four women deliberated over two days before reaching the verdict at U.S. District Court in Manhattan. The 76-year-old Taubman, of Bloomfield Hills, Mich., faces up to three years in prison.

"We are disappointed in the verdict," said defense attorney Robert Fiske. "We are going to review our options and decide what we will do next."

Former Sotheby's chairman Alfred Taubman arrived at federal court Tuesday with his attorney Robert Fiske (right).

Federal prosecutors had accused Taubman of scheming with his counterpart at rival Christie's, Anthony Tennant, to steal as much as $400 million in commissions paid by sellers from 1993 to 1999.

The prosecution's case centered on testimony by Diana Brooks, the former chief executive of Sotheby's, who pleaded guilty in October 2000 to price-fixing charges. She agreed to testify against Taubman in hopes of avoiding a three-year prison sentence.

Taubman, who is still the largest shareholder in Sotheby's, had denied the charges.

In his closing arguments, Fiske attacked Brooks' credibility, calling her a walking reasonable doubt. Fiske's team accused Brooks of single-handedly hatching the plot to fix prices on sellers' commissions during a February 1995 meeting in the back seat of her Lexus with her Christie's counterpart, Christopher Davidge.

Sotheby's executives also testified that Taubman was often bored by finance, and that he would doze off at board meetings.

But during testimony, both Brooks and Davidge said their bosses ordered them to end a costly rivalry by eliminating discounts and charging identical, non-negotiable commissions.

Former Christie's chairman Tennant could not be extradited from Britain for the trial, which lasted three weeks.

Together, Sotheby's and Christie's control over 90 percent of the world's art auctions. - from staff and wire reports